Hakushaku Reijou wa, Keiyaku Kekkon shita Ore ni Itsu Koi wo Suru?

The story of a beautiful Kingdom Knight wife with royal blood, and her husband, the plain seventh son of a poor Baron! Their love(?) suspense(?) story, beginning with a contract marriage, starts now! That marriage marks the beginning of the search for a culprit in an incident from thirteen years ago, swirling with secrets and conspiracies...

(Source: Gentosha, translated)